Platform-Specific Patterns

iOS and Android have real differences. RN abstracts most, but sometimes you need to branch.

Platform.OS

import { Platform } from 'react-native';

console.log(Platform.OS);                  // 'ios' | 'android' | 'web' | 'windows' | 'macos'

if (Platform.OS === 'ios') {
  // iOS-only logic
}

Platform.OS is set at runtime by RN. Use for small branches:

const elevation = Platform.OS === 'android' ? { elevation: 4 } : { shadowOpacity: 0.1 };

Don't fork entire components for 5 lines of difference — use Platform.select or inline conditionals.

Platform.select

Declarative platform branching:

const styles = StyleSheet.create({
  card: {
    padding: 16,
    backgroundColor: '#fff',
    ...Platform.select({
      ios: {
        shadowColor: '#000',
        shadowOffset: { width: 0, height: 2 },
        shadowOpacity: 0.1,
        shadowRadius: 4,
      },
      android: {
        elevation: 4,
      },
      default: {},   // web, windows, macos
    }),
  },
});

Each key returns a value; Platform.select picks the matching one.

Platform.Version

Numeric on Android (API level: 28, 30, 33, 34), string on iOS (e.g. '17.0'):

if (Platform.OS === 'android' && Platform.Version >= 33) {
  // Android 13+ specific behavior
}

if (Platform.OS === 'ios' && parseInt(Platform.Version as string) >= 17) {
  // iOS 17+ specific
}

File extensions

For whole-component swaps, Metro bundler picks files based on extension:

src/
├── components/
│   ├── DatePicker.tsx              # default for all platforms
│   ├── DatePicker.ios.tsx          # iOS-only override
│   ├── DatePicker.android.tsx      # Android-only override
│   ├── DatePicker.native.tsx       # native (iOS + Android, NOT web)
│   └── DatePicker.web.tsx          # web (RN Web)

// import is the same — Metro resolves to the right file
import { DatePicker } from './components/DatePicker';

Use file extensions when:

• The two platforms need genuinely different markup.
• Native modules differ per platform.
• Otherwise, prefer Platform.select or inline conditionals — easier to read in one file.

Native modules

Expo SDK (managed)

Pre-installed, no native linking needed. Just install the JS package:

pnpm add expo-camera expo-location expo-notifications

import * as Camera from 'expo-camera';
const [permission, requestPermission] = Camera.useCameraPermissions();

For custom native code in managed workflow, you need to migrate to dev-client or eject to bare.

Bare RN (autolinking)

RN 0.60+ has autolinking — installing a package via npm/yarn/pnpm wires it up automatically:

pnpm add react-native-camera
cd ios && pod install                          # iOS only — install CocoaPods deps

After install:

• Run npm run ios / npm run android to rebuild with new native module.
• Restart Metro (npm start --reset-cache if cached).

Some packages need additional native config (manifest entries, Info.plist keys). Check package README.

Custom native modules

Bare: write Objective-C/Swift (iOS) and Java/Kotlin (Android) modules. Beyond the scope of this skill.

Expo: write a config plugin that injects native code via the prebuild step. See expo-build-properties and withDangerousMod examples.

Permissions

Expo

Each feature-specific package handles its own permission flow:

import * as Camera from 'expo-camera';
const [permission, requestPermission] = Camera.useCameraPermissions();
if (!permission?.granted) {
  await requestPermission();
}

import * as Location from 'expo-location';
const { status } = await Location.requestForegroundPermissionsAsync();

Declare permission descriptions in app.json:

{
  "expo": {
    "ios": {
      "infoPlist": {
        "NSCameraUsageDescription": "Allow $(PRODUCT_NAME) to access your camera",
        "NSLocationWhenInUseUsageDescription": "Allow location access for map features"
      }
    },
    "android": {
      "permissions": ["CAMERA", "ACCESS_FINE_LOCATION"]
    }
  }
}

Bare

Use react-native-permissions for unified API:

import { check, request, RESULTS, PERMISSIONS } from 'react-native-permissions';

const status = await check(PERMISSIONS.IOS.CAMERA);
if (status !== RESULTS.GRANTED) {
  await request(PERMISSIONS.IOS.CAMERA);
}

Configure Info.plist (iOS) and AndroidManifest.xml (Android) with the right keys / permissions.

Safe area

The notch (iPhone X+) and rounded corners (iPad/iPhone) eat into screen real estate. iOS has the home indicator; Android may have on-screen nav bar or gesture area.

react-native-safe-area-context (preferred)

// Wrap app once at root
import { SafeAreaProvider } from 'react-native-safe-area-context';

export default function App() {
  return (
    <SafeAreaProvider>
      <RootNavigator />
    </SafeAreaProvider>
  );
}

// Use SafeAreaView in screens
import { SafeAreaView } from 'react-native-safe-area-context';

<SafeAreaView style={{ flex: 1 }} edges={['top', 'bottom']}>
  {/* screen content */}
</SafeAreaView>

// Or insets for fine control
import { useSafeAreaInsets } from 'react-native-safe-area-context';
const insets = useSafeAreaInsets();
<View style={{ paddingTop: insets.top, paddingBottom: insets.bottom }}>...</View>

The RN-built-in SafeAreaView from react-native is deprecated — don't use it.

edges prop: which edges to apply safe area padding. Often ['top'] for screens with bottom tab nav (tab nav handles bottom safe area).

Keyboard handling

import { KeyboardAvoidingView, Platform } from 'react-native';

<KeyboardAvoidingView
  behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
  style={{ flex: 1 }}
  keyboardVerticalOffset={64}                  // header height
>
  {/* form */}
</KeyboardAvoidingView>

For more control, use react-native-keyboard-controller:

import { KeyboardProvider } from 'react-native-keyboard-controller';
// Wrap app, provides better keyboard event APIs and animations.

Status bar

Expo

import { StatusBar } from 'expo-status-bar';
<StatusBar style="auto" />

style: 'auto' (matches color scheme), 'light', 'dark', 'inverted'.

Bare

import { StatusBar } from 'react-native';
<StatusBar barStyle="dark-content" backgroundColor="#fff" translucent={false} />

backgroundColor is Android-only; iOS uses the underlying view's color.

Pixel ratio and dimensions

import { Dimensions, useWindowDimensions, PixelRatio } from 'react-native';

// One-time read (doesn't update on rotation)
const { width, height } = Dimensions.get('window');

// Reactive — updates on rotation/resize
const { width, height } = useWindowDimensions();

// For native conversions (rare)
const px = PixelRatio.getPixelSizeForLayoutSize(50);

Use useWindowDimensions for layouts that adapt to orientation.

Common platform pitfalls

Issue	Platforms	Fix
Shadows differ	iOS uses shadowColor/Offset/Opacity; Android uses elevation	Platform.select
Status bar overlaps content	iOS by default doesn't; Android translucent does	Set translucent={false} or wrap in SafeAreaView
Back button	Android has hardware back; iOS doesn't	BackHandler (Android) for custom logic; React Navigation handles automatically
Date/time picker	iOS shows wheel; Android shows native dialog	@react-native-community/datetimepicker handles both
Keyboard appearance	iOS animates over content; Android may resize layout	KeyboardAvoidingView with behavior per platform
Linking external apps	iOS has stricter URL scheme rules	Linking.canOpenURL before openURL; declare allowed schemes in LSApplicationQueriesSchemes (iOS)
Push notifications	Different APNs (iOS) vs FCM (Android) tokens	Use expo-notifications or react-native-firebase for unified API
Notch / Dynamic Island (iOS)	Only iOS	SafeAreaView handles automatically

Anti-patterns

• ❌ Forking entire screens for Platform.OS === 'ios' when 90% of code is shared — use inline conditionals or .ios.tsx/.android.tsx only for genuinely different markup.
• ❌ Ignoring safe areas — content clipped by notch/home indicator.
• ❌ Calling NativeModules.X directly without Platform check — module may not exist on the other platform = crash.
• ❌ Using web-only positioning (position: 'fixed').
• ❌ Hardcoding pixel values without considering pixel ratio (use density-independent units; RN's "px" already handles this).
• ❌ Forgetting to declare permission usage strings in app.json / Info.plist — App Store / Play Store rejection.
• ❌ Assuming Android back button works without handling — BackHandler.addEventListener('hardwareBackPress', ...).
• ❌ Mixing the deprecated SafeAreaView from react-native with react-native-safe-area-context.